No Available Server (503) Error

If your deployed application or service shows a "No Available Server" error, this indicates that Traefik (the reverse proxy) cannot find any (healthy) containers to route traffic to under the provided secured URL (https).

What Causes This Error?

The "No Available Server" error occurs when:

1. Failed Health Checks - Traefik considers your container unhealthy
2. Domain Configuration Issues - Incorrect domain setup or missing www/non-www variants
3. Port Mismatches - Exposed ports don't match your application's actual listening port
4. Deployment Downtime - Brief downtime during container updates
5. Underlying Traefik Issues - Problems with Traefik itself (e.g., Docker API version mismatch)

Quick Diagnosis Steps

# SSH into your server and check container status
docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"

# Check proxy logs for errors
docker logs coolify-proxy --tail 50

Common Solutions

Advanced Debugging

Prevention Tips

1. Always Use Health Checks:

   • Implement a /health endpoint in your application
   • Ensure all dependencies (e.g. curl/wget) are available in your container

2. Test Locally First:

   • Test your health check endpoint before deploying
   • Verify port configuration matches your app

3. Monitor Container Status:

   • Regularly check docker ps for unhealthy containers
   • Set up monitoring for health check failures

4. Use Staging Environment:

   • Test domain configurations in staging first

When to Seek Help

If none of these solutions work, join our Discord community and provide:

• Application logs
• Coolify proxy logs
• Container health status (docker ps)
• Domain configuration screenshots
• Health check configuration
• Steps you've already tried

This will help the community diagnose more complex issues specific to your setup.